Does the sec approve companies' offerings of securities or prospectuses?
No. The SEC never evaluates the merits of offerings, or determine if the securities are "good" investments.
The SEC staff generally does review Registration Statements, but it does not independently verify their truthfulness or completeness. For example, the Registration Statements must contain financial statements prepared by certified public accountants. The staff of the SEC does not conduct its own independent review of the financial statements, and if they seem in order, that is the end of the matter. The same is true with other aspects of the Registration Statement. When the staff concludes its review, it declares the Registration Statement "effective" and the company issuing the securities may sell them.
The issuing company, its key officers and directors, and the experts named in the Registration Statement, such as the accountants, are responsible for (and liable in the event of) any false statements of a material fact, or misleading omissions.